Research On Four Simultaneous Axes Electromechanical Actuator With RSSR Spatial Linkages

Electromechanical Actuator (EMA) as an important part of the missilecontrol systems, whose performance plays a great influence on the dynamicquality of the missile. This paper studied the present situation in this field, proposed anew four simultaneous axes Electromechanical Actuator based on ballscrew and spatial linkage combined, and researched the effect of the dynamicperformance of the electromechanical actuator in detail caused by the motion pairswith clearances and flexible bodies. It proved that the program is worked bysimulation analysis and experimental comparison.This paper first determined the overall scheme of the electromechanical actuator,including the transmission scheme with ball screws and spatial linkage combining,and the double closed loop control scheme with speed and position. Itselected a brushless DC motor as the power input, and the first reducer is ball screw,the second one is four RSSR spatial linkages combined. It researched the influence ofratio and moment of inertia to the MEA. It selected the total transmission ratio of84.To increase the synchronization of four output shaft, kinematicresearch and the parameter optimization was taken out in four RSSR spatial linkagecombined mechanism. The result is the angle error between the four outputshaft ranges-0.143°to0.210°. Clearance and flexibility are the key issues that affect the dynamic performanceof mechanical systems. This paper mainly studied the effect of these elements on thedynamic performance. First a non-linear spring-damper contact dynamic force modelbased on Hertz contact theory was established to describe the contact-impact force,called Lankarani and Nikravesh model. Then study the influence of clearances to theimpact speed and contact force. The single and multiple clearances and flex bodies ofnonlinear factors on the dynamic performance of the EMA transmission system wereresearched. Studies have shown that: contact force is several times than ideal force,and the speed and acceleration generated huge fluctuations; when a branch in thesystem containing two ball motion pairs with radius clearance0.01-0.03mm, singleoutput shaft position error is±0.08o, compared with ideal motion pair. Whenconsidering the weak aspects, like circular shaft, linkages, etc. The output shaftposition error to±0.081o; through the analysis of the system frequency andexperimental test, it proved that system resonant frequency above100Hz and met thesystem requirements.Finally, a co-simulation was established with the flexible multi-body EMAtransmission system with clearances, based on ADAMS/Control and Simulink. Asimulation block diagram of double closed loop with position and speed was built,debugged controller parameters and executed simulation test, and the result was metthe system target. Finally, semi-physical simulation platform of EMA transmissionsystem was established based on Matlab/xPC environment. The result of the testshowed that, the EMA output torque is10Nm; the maximum rudder angle is±20o; themaximum rudder angle speed is250o/s; and bandwidth is23.17Hz. Each of theperformance were met the requirements.Through the study of the new EMA show that, the ball screw and RSSR spatiallinkage combined EMA is worked well. The work of the thesis provided a guidingrole in the theory and engineering applications on the new electromechanical actuatorresearch work.